Minor modification to official method 2000.13, Reveal for E. coli O157:H7 test system in selected foods (8-hour method): validation of the test for 375 g raw beef samples.

A lateral flow immunoassay for Escherichia coli O157:H7 (Reveal E. coli O157:H7, 8-h version), previously validated for 25 g raw ground beef, raw beef cubes, and lettuce rinse samples, has been validated for use in testing 375 g samples of raw ground beef and raw beef cubes. The Reveal method, including culture confirmation of positive immunoassay results, was evaluated in comparison to the current reference culture procedure of the U.S. Department of Agriculture-Food Safety and Inspection Service. For both sample types, the Reveal test with 12-h enrichment produced more positives than the reference method, although the differences were not statistically significant. Statistical equivalence to the reference method was also obtained at 10 and 11 h of enrichment for raw beef cubes and at 8, 10, and 11 h for raw ground beef, but maximum sensitivity of the method is only achieved after 12 h of enrichment. The Reveal method exhibited 100% specificity, with no false-positive results obtained on uninoculated control samples. It is recommended that this minor modification to Method 2000.13 be adopted Revised First Action.